JPH05291590A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a surface pressurized semiconductor pressure sensor in which excess silicon gel is sucked by using a jig by forming a recess to become a sucking region of an excess protective material on a residual surface of a bottom in a package. CONSTITUTION:A sufficient amount of silicon gel 7 is potted up to a level in which a chip 1, an external lead terminal 3 and wires 4 are submerged in a package, a vacuum evacuation type suction nozzle 9 is inserted obliquely sidewise into the package 5 in contact with a recess 8, and the gel 7 is sucked out. Thus, the excess gel 7 in which the chip 1, the terminal 3 and the wires 4 are buried is fluidized toward the recess 8, and sucked to the nozzle 9. When a thickness of the layer of the gel 7 covering the surfaces of the chip 1, the wires 4 is sufficiently reduced to about several tens mum, the sucking is stopped. Accordingly, an accuracy of a surface pressurized type semiconductor pressure sensor can be significantly improved by reducing the thickness of the layer of the gel covering the surface of the chip to about several tens mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface pressure type semiconductor pressure sensor mounted in a dual in-line package (DIL package), and more particularly to a package structure thereof.

[0002]

2. Description of the Related Art As a semiconductor pressure sensor, a semiconductor pressure sensor chip, which is formed by diffusing a semiconductor piezoresistor called a strain gauge resistor on a thin diaphragm formed on a part of a silicon substrate, is used to measure the pressure. It is well known that the above resistance change is converted into an electric signal and detected.

FIGS. 5 and 6 show an assembly structure (DIL package) of a conventional surface pressure type semiconductor pressure sensor, in which 1 is a semiconductor pressure sensor chip and 2 is a glass on which the chip 1 is mounted. A pedestal 3, an external lead-out terminal, 4 an aluminum wire bonded between the bonding pad 1a of the chip 1 and the external lead-out terminal 3, 5 a resin package, 6 a package lid, 6a a pressure guide hole formed in the lid 6, A silicone gel 7 protects the surface of the chip 1.

Here, the chip 1 is hermetically bonded in vacuum to the upper surface of the glass pedestal 2 with the concave space of the substrate having the diaphragm facing the lower surface. On the other hand, in the center of the bottom of the package 5, a cavity 5a is formed which is recessed one step lower, and the pedestal 2 on which the chip 1 is mounted is fixed to the bottom of the cavity 5a with an adhesive. The external lead-out terminals 3 are arranged on both the left and right sides of the package 5 with the cavity 5a sandwiched therebetween. The cavity 5a of the package 5 in the assembly structure is formed so that the chip 1 mounted on the pedestal 2 and the external lead-out terminal 3 are arranged at substantially the same height in the package. Further, the silicone gel 7 plays a role of protecting the chip 1 and the wires 4 and the like from dust and moisture that enter the package through the pressure guiding hole 6a.

The semiconductor pressure sensor having the above structure is assembled as follows. First, the cavity 5a of the package 5
Then, the assembly of the chip 1 and the pedestal 2 is built in, and then the wire 4 is bonded between the bonding pad 1 a of the chip 1 and the external lead-out terminal 3. Next, an appropriate amount of silicone gel 7 is potted into the package 5 to cover the surfaces of the chips 1 and wires 4, and the silicone gel 7
Then, the package 5 is finally covered with the lid 6 to complete the product.

[0006]

By the way, in the surface pressure type semiconductor pressure sensor as described above, when silicone gel is injected into the package as a measure for protecting the chip surface, from the viewpoint of maintaining the accuracy of the sensor. The following considerations are necessary. That is, since the silicone gel maintains the gel property even in the cured state, the pressure guiding hole 6a in FIG.
The pressure applied from the outside through the silicone gel 7 is somewhat attenuated while propagating through the silicone gel 7 on the way to pressurizing the diaphragm of the chip 1. In addition, when the silicone gel is subjected to a thermal cycle or when it absorbs moisture, its mechanical properties change, and its influence causes variations in the measurement accuracy of the sensor. Moreover, such an influence on the measurement accuracy becomes more significant as the thickness of the gel layer increases. Therefore, in order to improve the accuracy of the pressure sensor, it is necessary to make the layer thickness of the silicone gel 7 sealing the surface of the chip 1 as thin as possible.

Therefore, the inventors of the present invention potted the silicone gel 7 onto the package 5 to the level at which the wire 4 was first immersed in the chip sealing step, and then used the vacuum suction nozzle to remove the excess gel inside the package. Suck from
Finally, an attempt was made to reduce the thickness of the gel layer covering the surface of the chip to about several tens of μm. When the gel is absorbed, the wire is exposed on the gel layer, but since the gel itself is adhesive, the surface of the wire is covered with the gel. However, with the conventional package structure, as shown in FIG. 6, the wire 4 is laid between the external lead-out terminal 3 and the periphery of the chip 1, and the chip itself has a very small size of about 3 mm square. Because of this, handling the suction nozzle is extremely difficult. That is, it is extremely difficult to insert the tip of the suction nozzle into the peripheral area of the chip 1 without touching the wire 5. Because of this, the tip of the suction nozzle is erroneously
There are many troubles such as scratching the surface of the wire, deformation of the wire 4, and breaking of the wire 4, and it is extremely difficult to put the wire into practical use if it is left as it is.

The present invention has been made in view of the above points, and an object of the present invention is to solve the above-mentioned problems and to secure the surplus amount of silicone gel potted in a package in a chip sealing step with good safety and workability. It is an object of the present invention to provide a surface pressure type semiconductor pressure sensor which can be sucked by using a jig such as a suction nozzle, particularly a package structure thereof.

[0009]

According to the present invention, the above object can be achieved by forming a recess, which is connected to the cavity, in the remaining surface area of the inner bottom of the package and serves as a work area for sucking excess protective material. Here, the recess may be formed so as to be continuous with the cavity in an inner peripheral surface area of at least one of two opposite sides of the four sides of the rectangular package, excluding the two sides on which the external lead terminals are arranged. it can. Further, it is preferable that the bonding pad of the chip is formed on the peripheral edge of the chip other than the side facing the recess.

[0010]

With the above construction, first, immediately after potting the silicone gel as the protective material into the package, the recess formed in the side of the cavity linked to the cavity of the package is also filled with the gel. Here, when the vacuum suction nozzle is inserted into the recess to absorb the gel, the gel that covers the surface area of the chip, external lead-out terminal, wire, etc. flows in the form of being dragged by this and flows into the recess together. It will be sucked up. Moreover, this recess is a chip,
Since it is formed away from the cavity where the wires are located, there is no risk of the suction nozzle touching these parts, and there is a sufficient working space to allow the safe and efficient operation of sucking excess gel. it can.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings of the embodiments, the same members corresponding to FIGS. 5 and 6 are designated by the same reference numerals. First, in FIGS. 1 and 2, a cavity 5a for incorporating the chip 1 and the pedestal 2 is formed at the center of the bottom of the package 5 having a rectangular shape (quadrangle). Further, the external lead-out terminals 3 are arranged on the two left and right sides of the package 5 with the cavity 5a sandwiched therebetween, and the recesses 8 connected to the cavity 5a are sandwiched on both sides of the cavity 5a in the inner peripheral side surface regions of the remaining two sides. It is newly added and formed. The recess 8 is recessed to the same depth as the cavity 5a, and a constriction is formed at the boundary with the cavity 5a, which is necessary for positioning the chip 1.
On the other hand, the potting pad 1 formed on the upper surface of the chip 1
All of a are centrally arranged on the chip peripheral portions of the two left and right sides facing the external lead-out terminal 3 and wire-bonded between the external lead-out terminal 3 and the chip side facing the recess 8. There is no bonding pad.

In the case of sealing the surface of the chip 1 with the silicone gel 7 in such a structure, first, a sufficient amount of the silicone gel 7 is packaged in the package to the level where the chip 1, the external lead-out terminal 3, and the wire 4 are submerged. Potting on.
Next, as shown in FIGS. 1 and 3, a vacuum suction type suction nozzle 9
Is obliquely inserted into the inside of the package 5 and applied to the recess 8, and the gel 7 is sucked in this state. As a result, as the gel is sucked from the recess 8, the excess gel filling the chip 1, the external lead-out terminal 3, and the wire 4 flows toward the recess 8 and is sucked by the suction nozzle 9. Will be Then, when the layer thickness of the gel 7 covering the surfaces of the chips 1 and the wires 4 is finally reduced to about several tens of μm, the sucking is stopped.

By the way, according to the above construction, the recess 8 is formed at a position apart from the cavity 5a, and the bonding pad 1a of the chip 1 is not formed on the side facing the recess 8. Therefore, as described above, by inserting the suction nozzle 9 into the recess 8 and sucking the excess gel, there is no risk of touching the tip of the suction nozzle 9 with the tip 1, the wire 4, etc. The gel suction work can be safely and efficiently performed.

FIG. 4 shows an application example of the present invention. In this embodiment, as compared with FIG.
It is formed only on one side surface area of a. In this example,
Since there is only one recess 8, the work efficiency is somewhat lower than in the case where the gel suction work is performed by using two suction nozzles 9 at the same time as shown in FIG. Since it is a place, the external dimensions of the entire package 5 can be reduced. In the configuration of FIG. 4, the bonding pads 1a of the chip 1 do not necessarily have to be arranged on the right and left sides facing the external lead-out terminals 3 and are distributed on the remaining three sides except the side facing the recess 8. Even if they are arranged in the same manner, the same effect can be obtained.

[0015]

As described above, according to the present invention, the recess formed by the suction nozzle inside the package in the excess gel absorption step when the surface of the chip incorporated in the package is sealed with silicone gel. By advancing the suction work by inserting it into the device, it is possible to safely perform the work without touching the suction nozzle to the tip, the wire and the like. In addition, by absorbing the excess gel and finally reducing the layer thickness of the gel that covers the surface of the chip to about several tens of μm, the influence of the gel on the measurement accuracy of the pressure sensor is significantly reduced, and the surface pressure type The accuracy of the semiconductor pressure sensor is greatly improved.

[Brief description of drawings]

FIG. 1 is a plan view of the embodiment of the present invention with a package lid removed.

FIG. 2 is a sectional side view of FIG.

FIG. 3 is an explanatory diagram of a surplus gel suction work in the configuration of FIG.

FIG. 4 is a plan view of an application example of the present invention.

FIG. 5 is a sectional view showing an assembly structure of a conventional semiconductor pressure sensor.

6 is a plan view showing a state in which a package lid in FIG. 5 is removed.

[Explanation of symbols]

 1 Semiconductor Pressure Sensor Chip 1a Bonding Pad 2 Glass Pedestal 3 External Lead-out Terminal 4 Wire 5 Package 5a Cavity 6 Package Lid 6a Pressure Guide Hole 7 Silicone Gel 8 Recess 9 Suction Nozzle

Claims (4)

[Claims] 1. A semiconductor pressure sensor chip having a strain gauge resistance formed on a diaphragm of a substrate is mounted on a pedestal and incorporated in a cavity formed at the center of the bottom of the package, and the bonding pad of the chip and both left and right sides of the cavity are mounted. In the surface pressure type semiconductor pressure sensor in which the surface of the chip and the wire is sealed with a gel-like protective material while connecting the wire to the external lead-out terminal that is arranged, in the remaining surface area in the package connected to the cavity. A semiconductor pressure sensor, characterized in that a recess serving as a work area for sucking excess protective material is formed. 2. The semiconductor pressure sensor according to claim 1, wherein a cavity is formed in an inner peripheral surface area of at least one of two opposing sides of the four sides of the rectangular package, excluding the two sides on which external lead terminals are arranged. A semiconductor pressure sensor characterized in that a recess is formed so as to connect with the semiconductor pressure sensor. 3. The semiconductor pressure sensor according to claim 1, wherein the bonding pad of the chip is formed on the peripheral edge of the chip other than the side facing the recess. 4. The semiconductor pressure sensor according to claim 1, wherein the gel-like protective material is silicone gel.